* {
  box-sizing: border-box;
}

  p, h2 {
    margin: 5px auto;
    text-align: center;
    font-family: Arial;
  }
  table {
    border: solid 5px silver;
    margin: 10px auto;
    border-collapse: collapse;
    vertical-align: middle;
    text-align: center;
  }
  tr td {
    border: 1px solid #000;
    font-family: Arial;
    font-size: 150%;
    height: 8vmin;
    width: 8vmin;
  }
  .grille tr:nth-child(3n) {
    border-bottom: 3px solid #000;
  }
  .grille td:nth-child(3n) {
    border-right-width: 3px;
    border-right-style: solid;
    border-right-color: #000;
  }
  table.choix {
    border: none;
    border-collapse: separate;
  }
  .grille td:nth-child(3n) {
    border-right-width: 3px;
    border-right-style: solid;
    border-right-color: #000;
  }
  td:empty {
    background-color: white;
  }
  .buttonRound {
    border: 2px solid #88b6e0;
    border-radius: 5px;
    background-color: #aad7e2;
    color: #000000;
    font-weight: bold;
    text-decoration: none;
    padding: 10px 20px 10px 20px;
    display: block;
    margin: 10px auto;
    text-align: center;
  }
  .buttonRound:hover {
    border: 2px solid #3266f5;
    background-color: #daeef0;
  }